1. Field of the Invention
This invention relates in general to new and useful improvements in panels which may be utilized as modular office partitions and, more particularly, to an acoustic panel having desirable sound absorbing characteristics and which has fire-retardant qualities.
2. Description of the Related Art
Office space is often rented as a large open area generally without partitions. Normally such office space is divided into a number of smaller, more functional work stations, rooms and halls by utilizing semi-permanent panels of varying height in the form of metal frames joined together at their edges and having covered cores.
Movement of people through and around the work stations, rooms and hallways, conversations, telephone conferences, normal operation of office equipment, and business activities in general can generate considerable noise. The noise can be distracting to workers and visitors to the office and can diminish work place productivity. Accordingly, there is considerable need for panels that have the capacity to absorb sound and frustrate the transmission of sound therethrough. It is also desirable that these panels be fire resistant or retardant in order to meet local fire codes.
A number of attempts to make acoustic and fire-retardant panels have been made heretofore. Most of these panels have been relatively expensive.
Webster U.S. Pat. No. 4,441,580, issued Apr. 10, 1984, discloses an acoustical panel having air impervious septum, a layer of low-density fiberglass, a perforated layer of medium-density fibrous board having tackable qualities and an outer layer of fiberglass or decorative fabric. A steel rim surrounds the panel. Structured rigidity must be provided by the septum and the steel rim. This construction has relatively low torsional resistance.
The U.S. Pat. No. to Lapins et al. 4,630,416, issued Dec. 23, 1986, discloses a sound-absorbing acoustical panel which consists of a central honeycomb core that acts like a septum. On both sides of the honeycomb core a thin facing sheet of aluminum has holes placed in the skin forming Helmholtz resonators with the honeycomb core. The holes alternate between columns of the honeycomb cells which are open on only one side. Attached to the skins is a layer of porous sound-absorbing material, which consists of a thin layer of high density fiberglass and an outer layer of variable density fiberglass. The outer layer is of variable density fiberglass, from low density to more dense as it approaches the thin high-density layer. The decorative fabric layer covers a porous soundabsorbing layer. The sound-absorbing panel is enclosed in a frame of channel shape rails which presumably are made of metal. The Helmholtz resonators are difficult to tune to a broad range of frequencies and work best for narrow frequency bands. The panels require precise manufacturing tolerances and procedures.
The U.S. Pat. Nos. to Sailor et al. 4,084,366, issued Apr. 18, 1978, Sailor et al. 3,084,367, issued Apr. 18, 1978 and Sailor et al. 4,155,211, issued May 22, 1979, all disclose an acoustical panel similar to the Lapins et al. '416 panel.
The U.S. Pat. No. to Haugen et al. 4,702,046 issued Oct. 27, 1987, discloses an acoustical wall panel that mounts to a wall with a frame. The acoustical wall panel consists of a wooden frame that encloses fiberglass batts. Attached to the back of the frame is a plastic covering and in front of the frame is a rigid acoustical tectum board. An acoustical transparent cloth wraps around the wooden frame and is stapled thereto to cover the acoustical board. The Haugen et al. wall panel does not have the structural integrity required for partitions nor does it have the required sound barrier properties required for partition applications.
Herman Miller, Applicant's assignee, has heretofore manufactured and sold an office panel having a particle board frame, a honeycomb core, a hardboard layer covering the honeycomb board and attached to the frame, a scrim layer covering the hardboard layer and a decorative fabric covering the scrim layer. The scrim layer is a combination of a thin aluminum foil backed by a very thin layer of fibrous batting such as fiberglass. This prior panel has fire-resistant characteristics but did not have acoustical properties. The particle board frame is directional in nature. The pressed surfaces of the frame face outwardly and inwardly of the framing material so that the fabric can be attached to the outer surface through staples.
Herman Miller, Applicant's assignee, has also heretofore manufactured an acoustical panel in which clear pine rails and stiles form a frame, a hardboard septum is mounted within the frame, fiberglass batting is mounted within the frame on each side of the septum and a perforated steel panel was nailed or stapled to the frame. A layer of half-inch fiberglass batting is positioned outside the steel panels. A decorative fabric layer covers the fiberglass layer and is stapled to the outside edges of the frame. The clear pine frame elements were required to hold the nails or staples used to secure the steel panel to the frame as well as to hold staples used to hold the fabric to the sides of the frame members. The panels had a slightly puffy appearance.
The U.S. Pat. No. to Ashton, 4,571,906, issued Feb. 25, 1986, discloses a sectional screen in which a wood frame has a septum in a central portion, fiberglass batting in cells formed within the frames, a perforated wall on each side of the frame and a sound-absorbing cloth covering the frame.